Microfocusing source and multilayer-based beam generator for Mo Kα radiation

Two-dimensional multilayer optics have been widely used for enhancing and monochromatizing x-ray beams for various diffraction applications. However, when they are applied to Mo Kα radiation, the performance suffers from the fact that multilayer optics can use only a very small portion of the source. This is because the rocking curve of a multilayer becomes narrower at higher energy. Comparing to the optics for the Cu Kα radiation, the throughput of the optics for Mo Kα depends heavily on how small the source is. Based on the theoretical ray-tracing study, we have designed, fabricated and tested a system combining a microfocusing x-ray source and a side-by-side multilayer optic. Initial test results agree well with the theoretical expectation. The flux gain for a sample smaller than 100 micrometers is about 9 fold compared to a system composing of 2 kW sealed tube and graphite monochromator. The resolution of a diffractometer can also be improved by configuring the optical path. This paper will discuss the system design, detailed comparison between this system and a sealed tube-graphite monochromator based system, and possible applications such as small molecule diffraction system. A theoretical comparison to a rotating anode based system will also be discussed.